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ŠUMARSKI LIST 9-10/2022 str. 51     <-- 51 -->        PDF

Ribnik are selected (Figure 1). The high forests of the selected areas consist of mixed forests of beech and sessile oak, beech and fir with spruce and beech forests. Soil types range from deep and acidic to carbonate and dolomite soils as follows calcomelanosol, calcocambisol, luvisol and rendzina. As it can be seen, the high forests are diverse in the structure of tree species, plant communities, terrain and stand characteristics (Table 1).
The relative ratios of species are 59 % of beech, 29 % of sessile oak and 12 % of the other species of broadleaves in high forests with natural regeneration of MU Prosara. The relative ratio of broadleaves is 54 % and coniferous 46 % in high forests with natural regeneration of MU Bobija-Ribnik, and the ratio of fir is 33 %, spurce 13 % and beech 43 % respectively (Anon, 2013a, 2013b).
Research method is presented in the Figure 2.
2.1. Analysis of primary forest accessibility - Analiza primarne otvorenosti
The actual primary forest accessibility of forest area is usually expressed by density of primary forest traffic infrastructure, average extraction distance, relative primary forest accessibility and coefficient of efficiency of primary forest traffic infrastructure (Pentek et al. 2005, Sokolović and Bajrić 2013a).
Forest roads influence on the primary forest accessibility depending on its length, spatial distribution and extraction possibility. Poršinsky et al. (2017) defined four basic and five spatial criteria for determination of density of roads in forest. The basic criteria define the properties of roads which make a forest accessible. Spatial criteria determine an influence of roads on primary forest accessibility depending on their position in the forest area. The primary forest traffic infrastructure density is determined based on current length of forest roads, and in this investigation are recorded by GARMIN 62 ST hand held GPS device.
The second indicator of primary forest accessibility is extraction distance and it is observed like geometrical. The geometrical skidding distance is perpendicular distance from harvesting area to the forest road and it is shorter than the real one for value of skidding factor. The geometrical extraction distance is determined by method of Euclidean distance in ArcGIS 10. (Đuka et al. 2017). Harvesting technology that is most commonly used in BIH implies felling and processing of the trees at the stump by chainsaw and extraction of the assortments to the landing site. The most common harvesting method is the assortment method. Timber extraction is carried out by skidders mostly, so it can be spoken of a skidding distance (Marčeta et al. 2014).
Backmund (1966) introduced relative forest accessibility as an indicator of total forest accessibility, and it represents ratio between accessible forest area by primary forest traffic infrastructure and total forest area. That area is defined by width of buffer zone around of primary forest traffic infrastructure and it is equal to double targeted geometrical skidding distance (Pentek et al. 2005, Hayati et al. 2012, Sokolović and Bajrić 2013a). It is calculated by Equation 1: